What is a PRL? [Android A to Z]

What is a PRL? PRL stands for Preferred Roaming List and is a database used in CDMA (think Sprint and Verizon here) phones. It's built and provided by your carrier, and used when your phone is connecting to the tower. It indicates which radio bands, sub-bands, and service provider IDs will be searched for, then allows the phone to connect to the correct tower. Without a correct and valid PRL, your phone won't be able to roam outside your home network, and may not be able to connect at all inside the network. The database consists of an Acquisition table, which lists which radio frequencies to search for in which areas, and a System table, which tells the phone which towers it is allowed to connect to, and the preferred order.

Notice we said it connects to the correct tower and not the strongest tower. If you're in an area with weak but steady signal from your carrier, the PRL will connect you to that signal rather than connect to a stronger signal on a different carrier. When Palm released the Pre on Sprint (the first CDMA smartphone with "root" access to the system) people quickly learned how to hack the PRL to force a connection on Verizon towers in areas of poor Sprint coverage. The same thing is done today with certain CDMA Android phones, and usually ends up with the same result -- a letter from your carrier telling you it's been nice having you as a customer, but it's time to part ways. Not all hacking is good, kids, and when it adversely affects the network, it makes the other, good kind of hacking look bad.

The PRL is usually sent as an over-the-air update when needed, but often -- especially if you travel a lot -- it's necessary to manually update it. It's pretty easy to do:

Sprint: dial ##873283#

Telus: dial *22803

Metro PCS, US Cellular, Verizon (3G phones only): dial *228

Android phones also have an option to update the PRL in most CDMA phones, you'll find that in the settings pages. If you have a CDMA/LTE phone on Verizon or Metro PCS, your PRL will auto-update as needed, so don't fool with it. Also it's not a good idea to update your PRL while you're roaming on another carrier.

But the potential is there. Your carrier has to pay for roaming on the foreign carrier's towers. Since most plans now contain roaming at no charge, those charges are not passed onto the customer. If lots of people started doing this, it could end up being very expensive to Verizon and/or Sprint.

You can get booted for roaming on GSM networks as well, and you don't have to fiddle with your PRL to do so.

T-Mobile is famous for this. You get the zero-recourse notification and you are done. Don't bother to appeal, just go get another carrier.

If they can't make money on you, they will kick you off.

My Son had T-Mo for years and years in a town where they only had partial coverage, and none where he lived. He roamed on At&T most of the time. Since his old plan didn't have the "too much roaming" clause they let him stay, but 10 days after he adjusted his plan to a new version that included "too much roaming" clause they shut him down. Had he left it alone he would have been fine.

This is highly unlikely since the technology used by those two companies are not even compatible (CDMA vs. GSM). I will just assume you meant either Sprint roaming on Verizon, or T-Mobile roaming on AT&T.

You obviously didn't read the article:
"The PRL is usually sent as an over-the-air update when needed, but often -- especially if you travel a lot -- it's necessary to manually update it...
Sprint: dial ##873283#
Telus: dial *22803
Metro PCS, US Cellular, Verizon (3G phones only): dial *228"

I did love the roaming patch on my Pre. There was an area where we would go to stay from time to time and we had a problem with a ghost signal. The phone would say we were in a home area but it would never connect no matter how strong of signal strength. We complained to Sprint. They knew about it but wouldn't lift a finger because it was in a rural area. We used the patch there, forced it into roaming and we were able to communicate. It was a life saver in emergency situations.

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